The present invention relates to a control system for a motor, and more particularly to a control system for a motor that determines a ripple compensating current.
The output torque of a permanent magnet synchronous motor (PMSM) (either a surface permanent magnet (SPM) or an interior permanent magnet (IPM) motor) may be determined by a voltage command and a phase advance angle. A specific output torque of the PMSM is determined by first selecting a specific quadrature axis (also referred to as the q-axis) reference current and a direct axis (also referred to as the d-axis) reference current, and then determining the voltage command and the phase advance angle based on the selected quadrature axis reference current and the direct axis reference current.
Interior permanent magnet synchronous motors (IPMSMs) are relatively inexpensive, but typically produce a relatively high torque ripple during operation. Electric motors utilized in electric power steering (EPS) applications are generally required to produce relatively low torque ripple. Thus, the torque ripple produced by an IPMSM or an SPM may need to be reduced before being used in an EPS application. However, the effects of torque ripple compensation at relatively high motor velocities may be diminished.